122 CRUSTACEANS. 



of the intestines, directly into the blood, and is ready 

 for distribution, and for use in the cell construction. 



Tear a bit of liver to pieces in water on a slide, and 

 examine with low power to make out its structure. 



In the base of the head, in front of the mouth, are 

 two small excretory glands of light-greenish color. The 

 ducts from these open on the basal segments of the 

 antennae, as already noticed. 



IV. Nervous System. Find now the parts of the 

 nervous system. On the floor of the abdomen a longi- 

 tudinal chain of nervous ganglia will be readily seen. 

 Count the ganglia of the abdomen. Observe the deli- 

 cate white nerve fibers radiating from them. 



In the thorax, the chain seems to disappear in a sort of 

 canal formed on the ventral surface by the hard plates 

 arising from the floor, and forming a sort of internal 

 skeleton. These plates are for the attachment of the 

 powerful muscles of the legs and of the abdomen. By 

 carefully cutting away the hard parts that hide the nerve 

 chain, it may be followed forward to the head. A large 

 ganglion will be found just behind the esophagus, and a 

 larger cephalic ganglion or brain will be found just behind, 

 and a little above, the bases of the antennules. These 

 two large ganglia are connected by fibers passing on either 

 side of the esophagus, and forming the esophagal nerve 

 collar. From the cephalic ganglion, nerves may be traced 

 to the eyes, antennae, and antennules. 



V. Concluding Work. If any of the paired organs 

 mentioned have not been found thus far, they may be 

 looked for in what remains of this dissection (the left 

 side), or in another specimen. Finally remove carefully 

 the series of appendages belonging to the left side of the 

 body. 



Gather together in pairs all the appendages of the 

 body, in order, as follows : 



